SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84840c1adb4c660813b20a4003ae21ae408f4a4233df4b391116701a920c365b' 
  AND token = 'MOwfSjOJ1kKk9z3LShSYjvp7C+sHTu/eMsHlJhFcZgY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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