SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '305267268263937ec35c5fb5c16858a46aee35bf92b9ce899594453d174b2e85' 
  AND token = '8pSe31N+g4awY2/F6OwV8NJaj7/gAWyQASf0yFtb1dA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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