SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f9528d37f1cf6e2d5703bad9f6cf67ffc6a9588648a5c9fc6ff234bf04b0a87' 
  AND token = 'BScXYGS14h5CQ6JDxEqj+Qn/ZbI0I8JnDdmseW9/GjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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