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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '81c79bb8b29c46c3b710e52cd27f66f49e31bcfa25f73503ebfb51b7c91e4055' 
  AND token = 'xsO7RcmQux9nGY257er94IrV6fgbfsHzcsWBNagV48w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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