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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c42b02f8e65b5748363f1ed08dd00646bc72d1ea944201b5ea5beea48d2bdab6' 
  AND token = 'F+lS31l3NOVn3TxKGiqYxUBnyK434DU2blk2scTqenM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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