SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ec53497a3be5407738171cdcd0c3835d46ff586301f0f0aa3435c6a1b0829d0' 
  AND token = '08CHuOsxWtWWqfSBK3BFko+zlgsmYA2n8bUik/i4X78=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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