SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '378002392d51418cb67b0bffb70b2563705c3e48daa52c6a065fddff7ee14d92' 
  AND token = 'L1FGLR9ryh72XXq9NuZCienPpybL/356mLzWeWQeELQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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