SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fb37b3a202930cf240306ce64fd3fc17118de5336274aa1b682fd1de2019f45' 
  AND token = 'VjeymhrFOLcFA/L+fR9xcG2DKq2tkmIWBde1pyi3LzU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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