SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27bf6fb5b353e46da3ebb3877d2ce8e55f864e3afb2b22f90982a530f3f2e8ad' 
  AND token = 'XiszvRXAkXhiJPqj2uVmzBpJyXIr83HJZFYYM2juy+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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