SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dd508b82319aa987825a939f95214f3cbaec2e5dc34f5133f4ccc482354d2f44' 
  AND token = 'X/2VxI/HMHAtp6Ki+X43MXNMwNVOAWCd8RF/Ty3w3RI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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