SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e40c50973ed1db684ed59370162327b38cdaca258f36e178fcaacc434c499d10' 
  AND token = 'rnBrG3Po20VPNpBprSHrM5RiK16/fqItGo4MGjNlE24=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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