SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8766586066a3e175039b3fe6f5d57d843fa63f1907d1712932f90d5eab7a0a6' 
  AND token = 'OfvGlUywDZQhyGhu3OssXlFtY0oHEbOiQidiIR/ddzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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