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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff21b3aa7834023bd38d606e8823766e602449439433d81b8fa0bf2d9d16cb6e' 
  AND token = '9LkiibJCYAgrAuRXs1olbjei7tSx67etFb3jKDTJGnE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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