SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b21fcbeec46ae16736b06390c88cfba493e836d823f0751695d0634396db179' 
  AND token = 'kul7LtyMZvn1L/Y5T8h94O38aOz7ELyGqU47tuOhRd0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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