SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1c30827522659f57542f414affe2b1592e3b63e1cc273179f0bec7b3a573c6e' 
  AND token = 'LMetIL0yiRW81KUciAQXVQOb+8RbTrkdn23y651h1HY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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