SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e0a0009ed1a32a227581373f6fd17955556bb98f7c9bde4928d0b54e93d4c358' 
  AND token = '5ejcbYFhEGQiJCDULAwExRVE+CO1vuJwWKvYFzG/S7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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