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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b76719fc65357a20f8d23f409e2707f08a8726330c2bc78046000d9fcb62710e' 
  AND token = 'MSBEgXDIEgnAzOKY9UOmT2WV8RzlecoDB3VTgVK/FIQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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