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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'eb6b18a1f22d8e188fb51b082002731a60eab4c8babe465a21c3e85c9683c132' 
  AND token = 'vKQ8wTrMoZFC9CmfHaI6Ds/Vcq/mg7UPLMwKWOBieMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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