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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb19f896accd542fe00761e6e5c0099c750e23fce6b21d5d5134a7008bbf3644' 
  AND token = 'jB4Qsr9rhueB4ihnDaoZwM2/lV0ncmmTsoY/5djsviQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}