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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f294aa2dbd1f3695f166ec650bdcd79c70924eac6e6c80e6caf1d9b9ae84e9aa' 
  AND token = 'mYO366yU5EXO2wnmT/BXr7lXUCRlJp8jeEydGBh1ukM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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