SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51d17adfe85db40826aa458c7bbc7a1fe953331ab26c52b2ec925e88a0c2cf79' 
  AND token = 'J2mP0FwVZHWw0fIzCfa6QSJNzPVjjAZYYEqpGgdBeAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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