SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '502b8a3beaa05d86a377154b6c99c6af17bcb8ef45f41abf25be17438a3a2c86' 
  AND token = 'el/cmT6JOw0Egqej5o9gHL+YEgMGVHzrHoruj9u3VEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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