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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21eaa92542c46e3dd78da5e05769a2c9320df95b6c09e690b7994bc07fd51013' 
  AND token = 'UlSOBOieONpt6UsvPOOy6PVIEOyeg+fYM4ww2cbn/Lw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}