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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dcb2ad38229cbf6e56084d0a161f8643e8c6925f286755bd1330fc1249350a1d' 
  AND token = 'BMVPQ75EBEdBpllQ3ChUekxTwBjnAPRoo3xukClg4rs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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