SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e5e1c405847256011fbebee092b455f0c68e6dcf809aca8b58894fd24806eda' 
  AND token = '6mjEM8Fk8drZpH/DvfHsCkY6FUdkjL02Nom6CzcaJqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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