SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5541db46c8cb6763c72f1196ea75786f4d01775506e62a71baf59dce0f47298f' 
  AND token = 'PHy51zqbK9+rUOwSRWoKrsBEByj3CoXpjLmIOHkVRwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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