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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b298d818ac10a19350f201d1c2c14a5b0557f22da89796fa7365eee67546d249' 
  AND token = 'QNsQ+RAfQrU18kzN6D+fqM3+Xs5+qgARj+BvWgElYtE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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