SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2c6dc5fa746a403d634d1bd93cff5b4039996f598d1c4fccaa1a674b515efbd' 
  AND token = '3YfV9ehCVyt3k23TyVR5wwkkiPfadSuZ9vQPN+ISfUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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