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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29690402eefae51c7802dce381ff949358f3d06457354239e865d71b0079bba0' 
  AND token = 'yUsPboMj9ezjNoyBvVonEdTb0MC4LzhU+0MkyZqmnmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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