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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b7e5d8304b3faf5149fee4c1c7270d325a99e5c503e9a19b0478e45592a9437' 
  AND token = 'RZ4k8/UTZ9N9mU2cbAjRLKHmLiZ18jPizeHue8cC3WQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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