SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8340280f1f39e94559c722a4539cf442bbf4b3892361c62c5c29cc56c267e4e0' 
  AND token = 'j63EDgNw53HokMHbGDjLExfaBMW1szup3xGIkIW/VMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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