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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9ad68dc8ae6739e2e61621a2337d9554fe0c1b5a13b24cb5af088382560f5c50' 
  AND token = 'eR3lzWiT+i4r4bTfaW8dVH1Ppd8iGwIJck5dzk3ZXmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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