SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '575c98db24bd4b643db1aa5af0f8a592fdc78174ed684441b7476109b9644242' 
  AND token = 'VutL9j7sxDP2dwAA44+mcE5p9FRQAqIsTBx87wcUtF4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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