SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d9b06e3ff313698bf9917a1f172f6146d0585a2068ca2bcbfaa9b06ee103d8b' 
  AND token = 'vpwpJ9LHXjAHu7n6m2NBYzxZ+NZO+ToVp1Zvq8Ugdi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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