SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e2fd9f578b74edd09c9a837d789ff0897991d51d329464850d51067ccedff8' 
  AND token = 'zeoqQS3EZxgtRwDAuaWX6XhTq/sizZWpyR3iU8WK+6s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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