SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d2ff25fbf10ee6736769695a07b96423ec54a2022730ebc0b0aa956d02bce7' 
  AND token = 'q8Lwj4qpJ4jF7XzmpGP2QGGPxvF7Djlq1soLR+iF3Ik=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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