SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4849ec76fe4fcd27ceeaff86fef752379b363eb97609894db0e582be2a11a3d4' 
  AND token = 'ZViNtTAMe/hU7L9sozPg4A/SPyeaMaYEw9CQd8d5kSc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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