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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3b62fece8f85981ec5cfe0f5a14b5f78ea50aa6a288514a08506607ffc5b541' 
  AND token = '4MxoIR+RQKW0aVlx7gVEXKks8e+yhmPqxlIT8HqVI+8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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