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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4892e68f1cdf65eed3f4d2c46a4d0d033736fe9e1f0122c5aee72ac1ff1d9fa' 
  AND token = 'r0ldMOlxDJDYOnE+wwgZ5xeiahKuGDmqztcWBoYN6TM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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