SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '320bc398b08256889ecaeeb2a812c190aa674d593657b807f1dae80224f6e5a4' 
  AND token = 'Be2XgCNRRaqw3UMSBwo8OMofqDWM6T/aaYsRiUVdvmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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