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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c0d9d0d67f79ce516ff7a638a74567965da35cc2142aa27291a9ccc7687ea13' 
  AND token = 'XKektGfFtq7P8aorrxGZBsyTwiAf2RZ2+0AtU8SdgOI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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