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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a279aa926f649c17fd0fa33cdf5ccbc0be9b8d450892fc460c7a752750b0d447' 
  AND token = '/5rQGnd1ET2YH+lDx1WGmftzRMlmK/uFUM9NldwNf30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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