SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '568f754691d82745f3bc0568b6f339e78fcc94b1e4e29a27aa2b0626c53bfdce' 
  AND token = 'gBpU/CByEM45aU27qfVJ+XMW/byXUCIoMx1Z6FjOKp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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