SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21c598a952e4d2dff6969b7ae97e23eb4956a42869f9a1f86effb1f436e0d2c' 
  AND token = 'YojL2rwbL+ppRCQSC3cDmp0kW1K6gZ+i776quGr1JL0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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