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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c6825252eaf6c0bbb9d0c4568cbf1f175e94aef0485591c3178c83e19eb304' 
  AND token = 'clqJiYonQdZ7d2/fLk7YVL874yhAoCLbaZTBGAV5rnI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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