SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6a35b12f8ad71d1337669d70ae142a47fd286becea1ccb07bb942ae7b9ba62b' 
  AND token = 'RNjrVaAUaeDeqN4lVitgDVOKw9hzp6UJtrPHR6uyR0I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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