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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a24b7967cfd56cc0e7553620f3dcf75349b5eec7a358abe1925a656fc931a57' 
  AND token = 'QAIOcEmT1dNdYxPfbsIk+gTWV9kZ4NbkYJr/pIvYaJ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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