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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6d3d2958910e6ee7a1005100b3e4926d085ec73f636f34635eb655ebf90aed1' 
  AND token = '76S9E4Py700JXnmpl7bkVGC7SCPHwui0ekznCgW1p5I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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