SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '785023946eaf54545fb73167f3a31b18227a3dd894f335a4d7f266d86a0a3b17' 
  AND token = 'QWdfiNINqCO2DfVNFtS42GgTyB1sgHullhjeHeQiCz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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