SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '030d621a19901384edb601768fa288df69c3e387c732f774b39156b8ffe7d63f' 
  AND token = 'z8YXEt53IRETiuy/qMFTlF70igMH3CYnawyzfUjPTj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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