SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6455bcb2814386801570246db1042709faff37d80526e567fab4c40122eba0a2' 
  AND token = 'RkS7LJ3SxWrlFRCLLNo/WBhxfaHcgaBuOsAHw2v9DcY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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