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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b51992850ec9c81bb77fb4fcb134ce11c60c4b670851ce2a9bb989f25fb51506' 
  AND token = 'YvVYBronNdWUCGQAPu8F0hxNjCRChinno/nU316ekcY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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