SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f67936c685db948f1ac1fcf05cbe528e048af83be4c659a064aa689a3a0ead0b' 
  AND token = 'N9Q9gTjhHGjVcq1Tc9ty4AGOMKvg/ShHKYwv2t2sCzw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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