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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29a264bc5060a967dd005a09461f9e6e64603c99e259e8646a6ee5cdee01c3e9' 
  AND token = 'uA3ujj2JqFPkJHE1rUC1mN/Hfn2NPnTG/EH3ekccsDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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