SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b5f27b5d84e40262a50c082524b9ab75b46f5261784ebf0a98525df750d63c4' 
  AND token = 'MzSeeJLo3IApnLfZkBwP2OU2MuI58fhxWmXiyOkmvF0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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