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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e68d7b5f6599bff51886a73046db9c1e552585b315809584138c2a63435eadc9' 
  AND token = 'CTFPg5fvSlCfd15GRXEK46q7gBlSfzXDN/cidAGQfBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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