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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b253d18548987cfa1728deb79c7045109c74d3d38cdbca2faa3971ef042b89cb' 
  AND token = '39hj14F0S3Qpq021ii99Xg8s1zzExV5d+rjQpJcfAYY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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