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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e609cf6dd3ed6cd95fbf8d8e71a86d7748f97220c20a939b431efed761b81270' 
  AND token = 'S0v+QSicUBdI7BMUfsKFLNCPK1kkytpxfxB4UOT8P2I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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