SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a9f91dad4d14642397599440a7b9dfccf034e6c237581343a2777e11c5daaec' 
  AND token = 'sPQ/2vFEZPddvwkkEEJWnYC9Wukf3VMIlehXNhkboAA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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