SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b37576811383a4fbf46999dbe1e0d657b134347e7d8e0bbf42bbf244f9d88286' 
  AND token = 'OwsKnPiHy5k5mFtkZJ+epGpqbD36X+d+dOMBSpMRG34=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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