SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc1c84b18b8b2a95d4a8006a0abc4bcea66f4b844ba4635c502c5d1194a8843e' 
  AND token = 'lsiBxDMnMCXiJ+u2B8NFpQGyCO+/ibtvpO4JFIoCZdQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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