SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55748aa74a9a20c0c3869b571a186c34fbc6ac816f58266f6a1012e243acf500' 
  AND token = 'jKYivOf+Z37mWTzbsd1JoX45dZWTHcMcAC/5eIvrkk8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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