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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '611ab92d56aae913140c9e584131d6010c393abf248b21fe22929b2e4ee77044' 
  AND token = 't+UY6vy655rIkR9RdDTgmCQepEdxgp+AZeT16Ank/+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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