SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15bb8e6fdbdbc499e7e2f58b6cade7ab1c45da94ca16113c5697378a00ecf98' 
  AND token = 'rv1GZm66OPsc/1AaVBMmxXIrnOxqb1LCrV6b/4V+/sU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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