SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ca7eed035007a55a220c83192ea5c7ff495a504e1811c86f099b837ac90d5d8' 
  AND token = 'ProeP//7ae/iOybEIak9RLP4uelglucxIiu5mPF8TwU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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