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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6741cf5f65f95b52ff57da8f09a54387114b1e04a3cef50d4601e873c0a03be' 
  AND token = 'rtDAcffzkFgOElWOpsz6fUfeE98TxivCMOozLY85c+c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}