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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4192495a0b8029aa41f8aae6b670e1db83d5ed2f1f3bd29c4efdefc67e56a10' 
  AND token = 'ZUFGVbHk1J/vL4K0oMkfVtcn+2+aT1pHVbHjb964Gdw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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