SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8790dc47518ac0f41f5b3b3dcaf9feba1c39626141827636738378fd32a7385' 
  AND token = '/FQOjxqkmlaVx9ynZykkJdpKVEGAnzKintlJapEMEDs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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