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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9c973f450986edbc6e349d80cc3f228503cdc7aa1d4b5d0283f9b8cf7c29d9c' 
  AND token = 'A4731Lr/a5wMFxCI/UDUND5Bdi6eDx2MgUk/XQlEc1M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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