SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4a2811b7a213a2f947362089460b1eed94f1923ea76110d00bbbccc23cbda90' 
  AND token = 'fyQMuWqPNVSimPJm3vqg2KXyM6dOrktre/TRMJhlF2g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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