SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '847a7ac147c5466132cb24e7186e52de28a314699d78503fd15deb2b95f8dd5a' 
  AND token = 'FQevk+vKZq5c+Ax+kFCU3OYNhMkDo4mlna+J5yxMjoU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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