SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6393f972f1cd57d51fe94419b88a1831ecdff34215c618436ca8cf1522e6f909' 
  AND token = '8zbOoblYNwBLDRtJ+jpO1IReZfKhlngTibRbWnYMtZo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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