SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8978af4736af87018204ea96e3d6b220976568a48d0e9b6e315c4cdf5b9b60c' 
  AND token = 'BRq0YEFsujnOVG0m/4ly9A/46imuwdsKKUTwTLUfW/4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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