SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d97ee0fee5aab1b56bb479f6bea423475e043c92dd0a965968c6276bcb19ca7' 
  AND token = 'e/YiZbNI8Dyi2FKCRv8nt4sb2aL2Zm7HDHvlfi2UpS8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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