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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b68a51ff61eddf8df4b7d254b96ee3e2c2b4e671f1cd99aeb5568c674ef303f5' 
  AND token = 'GR6crDUjy5WPIL+KukjTUCvVLgStgLtRNh+kaHCQ6C0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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