SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '790de9706a125dc6c31c897e70f9ca0c47f530249109f8f5537bae944e77f428' 
  AND token = 'JHueahbPO2QiiQoVurFRpPHs7vhU0mPUCqRtzyRZfSo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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