SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b803d16567393294017c74622d24caae477aeb1e10ad246b6c5b3514c30808af' 
  AND token = 'lnqFA8aPCfSLLK/QJqiv068452/+NbMouPw3hTZsQWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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