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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfcfd6b3eb805b571fd2bf40104c7cefd7ea30cd6e6d2f7eccbdaec70f73b3c3' 
  AND token = 'Fuq3+ODb2FiKzDfgh3aDmEimvPJx1bLQYhcCMghJDY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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