SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c976d8c2ca693e63518d013b287327c6fcd87fe93fabcde6063d810b5c429785' 
  AND token = 'bvkqWylQaIwULAuksKTiUQMreBReBFz1CtJGAx32JAs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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